Intramolecularly Hydrogen-Bonded Aromatic Pentamers as Modularly Tunable Macrocyclic Receptors for Selective Recognition of Metal Ions

Despite
the tremendous progress that has been made in macrocyclic
chemistry since the discovery of corands, cryptands, and spherands
more than four decades ago, macrocyclic systems possessing a high
level of controllability in structural configuration concurrent with
a systematic tunability in function are still very rare. Employing
an inner design strategy to orient H-bonding forces toward a macrocyclic
cavity interior while convergently aligning exchangeable ion-binding
building blocks that dictate a near-identical backbone curvature,
we demonstrate here a novel pentagonal framework that not only enables
its variable interior cavity to be maintained at near-planarity but
also allows its ion-binding potential to be highly tunable. The H-bonded
macrocyclic pentamers thus produced have allowed a systematic and
combinatorial evolution of ion-selective pentamers for preferential
recognition of Cs+, K+, or Ag+ ions.